题干

将紫色洋葱表皮细胞置于0.3 g/mL的蔗糖溶液中,推测下列现象合理的是(  )
①液泡逐渐变小,颜色由浅变深   ②液泡逐渐变大,颜色由深变浅
③原生质层与细胞壁逐渐分离形成球形小团④原生质层与细胞壁之间是蔗糖溶液

A:①③

B:①③④

C:②③

D:②④

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答案(点此获取答案解析)

B

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    "Homestay is a form of study abroad program. It allows the visitor to rent a room from a local family to better understand the local lifestyle. It also helps to improve the visitor's language ability," said a teacher during a school meeting last term. "Students who wish to learn more about foreign cultures or to get foreign experience should join this kind of holiday. I am sure you won't be disappointed."

    After this special meeting, I always thought about this kind of holiday. Last month, I had a chance at last to go on such a holiday with some of my schoolmates and we went to London, a place where I had wanted to go since years ago.

    As we were still young, we had a group leader who planned things for us and looked after us. After we got to London, we went to stay with different families. I was lucky that my host family was a white couple who had a daughter about my age. They treated me as a daughter of their family during my stay there. They were interested in me and I learned a lot of things from them, too.

    The holiday was filled with activities every day. After breakfast, a local teacher would come to take us in his car. Then we would have classes or go on a sightseeing trip to different places of interest like the Big Ben, the London Bridge, and the Buckingham Palace. We would go back to our own homes after the activities

    The holiday was a valuable experience for me. I enjoyed every minute of it. Yet, time really flew fast. Three weeks later, we had to leave "home" for Hong Kong.